Cartridges containing single rigid magnetic recording discs are widely used in electronic data processing equipment. One such cartridge contains a flat aluminum disc having a large central opening bridged by a flexible stainless steel diaphragm which has a central spindle opening. The corresponding disc drive has a turntable including a magnetic ring that magnetically latches to a cold-rolled ferromagnetic steel collar on the aluminum disc. Fixed at the center of the turntable is a tapered spindle. The spindle opening in the steel diaphragm is slightly constricted so as to fit snugly onto the spindle before the disc becomes magnetically latched to the turntable. The flexibility of the diaphragm permits the disc to continue to move into the latched position until it fits tightly against the turntable while being held by the spindle against any radial movement.
Other current hold-down mechanisms for rigid magnetic recording discs are believed to be about as expensive as that described above. Mechanisms for positioning rigid optical recording discs are also expensive.